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PHP :: Bug #34199 :: SimpleXMLElement is Schroedinger's Cat

Bug #34199 SimpleXMLElement is Schroedinger's Cat
Submitted: 2005-08-20 21:13 UTC Modified: 2005-09-15 16:34 UTC
Votes:3
Avg. Score:3.3 ± 1.7
Reproduced:1 of 2 (50.0%)
Same Version:0 (0.0%)
Same OS:1 (100.0%)
From: rasmus@php.net Assigned:
Status: Closed Package: Scripting Engine problem
PHP Version: 5CVS-2005-08-20 (CVS) OS: *
Private report: No CVE-ID: None

 [2005-08-20 21:13 UTC] rasmus@php.net

Description:
------------
An empty SimpleXMLElement object is both true and false

Reproduce code:
---------------
$xml = "<root></root>";
$xml = simplexml_load_string($xml);
$kids = $xml->children();
if($kids) echo "True";
if(!$kids) echo "False";

Expected result:
----------------
False

Actual result:
--------------
TrueFalse

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 [2005-08-20 22:33 UTC] rrichards@php.net

if ($kids) if handled by ZEND_JMPZ_SPEC_CV_HANDLER which ends up calling i_zend_is_true and returning TRUE because $kids is an object.

if (! $kids) is handled by ZEND_BOOL_NOT_SPEC_CV_HANDLER which calls convert_to_boolean and ends up calling the objects cast_object handler, which in this case is sxe_object_cast and returns FALSE because object is really empty.

 [2005-08-20 22:53 UTC] rasmus@php.net

Marking it critical.  I think we need to get this cleaned up before 5.1 goes out.  Having 2 different opcodes handling this that can potentially return conflicting results causes all sorts of confusion.  Took me about an hour working backwards through assumptions before I finally figured out that if() and if(!) were to blame.

 [2005-08-23 03:56 UTC] sniper@php.net

This outputs nothing with PHP 5, but does give "yes" with 4.4:

<?php
$foo = new StdClass();
if(!$foo) echo "empty object: yes";
?>

So in PHP5, an "empty" object is still true.
(then again, empty array() is considered false)
Was the change intentional? And if so, why?

 [2005-09-12 13:54 UTC] dmitry@php.net

Fixed in CVS HEAD and PHP_5_1.

Now we call cast handler in both situations.

According to Jani's question - yes.
In PHP5, an "empty" object is true.
However you can use "zend.ze1_compatibility_mode".